1. Field of the Invention
The present invention relates to a peptide which inhibits the binding of human IL-6 (interleukin-6) to human IL-6 receptor; to a human IL-6 suppressant, an anti-inflammatory agent, an immunosuppressant or an anti-autoimmune disease drug containing such a peptide; to a gene which encodes such a peptide; to a plasmid carrying such a gene; to a transformant containing such a plasmid; to a method for the production of such a peptide by culturing such a transformant; and to a method of treating various diseases by administering such a peptide or a pharmaceutical composition containing such a peptide.
2. Discussion of the Background
Human IL-6 is a substance whose gene was isolated in 1986 (Nature, vol. 324, p. 73 (1986)). Human IL-6 is produced by a number of different types of cells, including monocytes, T cells, B cells, vascular endothelial cells, fibroblasts, and the like, and is known to have a variety of physiological effects, such as the induction of the differentiation of B-cells into antibody-producing cells, the induction of acute phase protein synthesis by liver cells, the induction of the differentiation of cerebral nerve cells, the induction of the proliferation and differentiation of hematopoietic cells, etc. (Jikken Igaku, vol. 7, No. 1, (1989)). Also, attention is being given to the participation of human IL-6 in various diseases, and many reports have been published in regard thereto.
First, reports regarding its participation in autoimmune diseases, include a report that the human IL-6 concentration in the synovial fluid of chronic arthritic rheumatism patients is extremely high in comparison with that of osteoarthritis patients (European Journal of Immunology, vol. 18, p. 1797 (1988)), that the autoimmune disease symptoms were improved by removing the primary tumors of cardiac myxoma patients which constitutively produce IL-6 (Proceedings of National Academy of Science, USA, vol. 84, p. 228 (1987)), and that in the case of Castleman's disease which is characterized by high .gamma.-globulinemia, a high concentration of human IL-6 was detected in the supernatant of affected lymph node tissue cultures (Jikken Igaku, vol. 7, p. 50 (1989)), etc., and of the so-called autoimmune diseases of which autoantibody production is thought to be a cause or aggravator, those with which IL-6 is strongly connected are thought to be the most dominant.
Furthermore, in the area of cancer, tumor cells taken from multiple myeloma patients constitutively produce IL-6, and their growth is further promoted by adding IL-6 thereto, which has led to a report that IL-6 is an autocrine growth factor for multiple myeloma (Nature, vol. 332, p. 83 (1988)), and to the suspicion that IL-6 is a growth factor for other blood tumors as well, including Lennert's T lymphoma, B-type chronic lymphocytic leukemia, etc. In addition, there is indication that the metastasis of different kinds of cancer cells to the liver in mouse models is correlated with the IL-6-producing capability of those cancer cell strains (Japanese Journal of Cancer Research, vol. 82, p. 1299 (1991)), and further indication of a strong correlation between IL-6 and cancer cachexia from the fact that high levels of IL-6 were shown to be present in the blood of tumor-bearing mice (Journal of Immunology, vol. 143, p. 162 (1989)), and that body weight loss occurred in nude mice which have been inoculated with CHO cells (Chinese hamster ovary cells) carrying the mouse IL-6 gene (Endocrinology, vol. 128, p. 2657 (1991)).
In the area of infections, there have been many reports regarding the connection between IL-6 and bacterial infection or viral infection, such as that the IL-6 concentration in the blood of patients with septic shock was extremely high, and patients with higher levels of IL-6 in the serum showed a lower rate of survival (Journal of Experimental Medicine, vol. 169, p. 333 (1989); Blood, vol. 74, p. 1704 (1989)), that the mononuclear cells of fetuses suffering from intraamniotic infection produced large amounts of IL-6 (Clinical Immunological Immunopathology, vol. 55, p. 305 (1990)), that IL-6 was present at high levels in the cerebrospinal fluid of patients infected with the human immunodeficiency virus (HIV) (Journal of Neuroimmunology, vol. 23, p. 109 (1989)), and that cells derived from Kaposi's sarcoma frequently seen in AIDS patients constitutively produced IL-6 or proliferated in an IL-6-dependent manner (Proceedings of National Academy of Science, USA, vol. 37, p. 4063 (1990)).
Furthermore, in the case of inflammatory diseases, the possibility has been suggested that IL-6 acts as an autocrine factor in mesangial proliferative glomerulonephritis, based on the fact that IL-6 was produced by mesangial cells derived from mesangial proliferative glomerulonephritis patients (Journal of Immunology, vol. 143, p. 3949 (1989)), and that the proliferation of mesangial cells was observed in IL-6 transgenic mice which constitutively express IL-6 in a B cell-specific manner (Proceedings of National Academy of Science, USA, vol. 86, p. 7547 (1989)). Also, high levels of IL-6 in the serum and IL-6 production in epidermal tissue have been reported in patients with psoriasis vulgaris, a disease involving the proliferation of keratinocytes (Proceedings of National Academy of Science, USA, vol. 86, p. 6367 (1989)). In addition, IL-6 is also said to contribute to the various symptoms of inflammation, such as fever, chills, malaise, etc. (American Journal of Physiology, vol. 258, p. 798 (1990)).
In addition to the diseases mentioned above, IL-6 is also suspected of playing a role in various other diseases, including Alzheimer's disease, amyloidosis, I-type diabetes, hyperlipidemia, osteoporosis, polycythemia vera, thrombocythemia, myocardial infarction, and the like.
Thus, human IL-6 is suspected of being a cause of numerous diseases, particularly inflammatory diseases and diseases involving the proliferation of lymphocytes, or there is a high possibility of human IL-6 being involved in the aggravation of such diseases. Therefore it is thought that suppression of the activity of human IL-6 may provide a treatment of those diseases.
In fact, regarding some of the above mentioned diseases, the suppression of IL-6 in mouse model experiments has led to improvement in the diseases. For example, it has been reported that, by the administration of anti-mouse IL-6 antibody or anti-mouse IL-6 receptor antibody, which have an effect of suppressing the activity of mouse IL-6, to mice inoculated with myeloma cells, it is possible to both suppress the growth of myeloma cells and raise the survival rate of the mice (Journal of Experimental Medicine, vol. 172, p. 997 (1990)); that the metastasis of tumor cells to the liver may be suppressed by the administration of anti-mouse IL-6 antibody (Japanese Journal of Cancer Research, vol. 82, p. 1299 (1991)); that even mice infected with a lethal dose of E. coli survive when they are preadministered anti-mouse IL-6 antibody which suppresses the activity of mouse IL-6 (Journal of Immunology, vol. 145, p. 4185 (1990)), that when anti-mouse IL-6 antibody which possesses mouse IL-6-suppressing activity is administered to mouse models which develop cachexia when inoculated with tumor cells, an improvement is observed not only in the weight loss, but also in the symptoms of the cachexia (Journal of Clinical Investigation, vol. 89, p. 1681 (1992)), etc. These facts directly indicate that IL-6 is connected with the above mentioned diseases. They also indicate that if the activity of human IL-6 can be suppressed, then a way may be provided for their treatment.
Methods which suppress the activity of human IL-6 include a variety of methods such as the inhibition of IL-6 production by IL-6-producing cells, inhibition of the binding of the IL-6 produced to receptors on the IL-6 response cells, and inhibition of IL-6 signals to IL-6 response cells. The methods of inhibiting the binding of human IL-6 to its receptors on the human IL-6 response cells are thought to be capable of selectively suppressing only the function of human IL-6 and thus, in consideration of their clinical application, to have the least number of side effects. Nevertheless, no medicines which specifically inhibit the binding of human IL-6 to human IL-6 receptors have been hitherto known other than mouse monoclonal anti-IL-6 antibody and mouse anti-IL-6 receptor antibody. However, these antibodies, which are the only ones known, are foreign proteins prepared from mouse hybridomas, and their constituent components are mouse proteins. Therefore, when they are administered to humans, an immune reaction is raised against the mouse protein, causing serious side effects such as anaphylactic shock, serum sickness, etc., and their effects are reduced due to the production of neutralizing antibodies against the mouse protein. Thus, the clinical application of mouse-derived antibodies for patients is fraught with difficulty. Therefore, at present no substances are known for the specific inhibition of the binding of human IL-6 to human IL-6 receptors which are suitable for clinical use, and thus it has been desired to develop clinically applicable medicines which inhibit the binding of human IL-6 to human IL-6 receptors as treatments for the above mentioned numerous diseases.